Transcript Physics for the Sciences 07:150:193 Fall 2003

A process is described mathematically:
m
m 
m
m 


M
(
0
)

4
M
(
5
)

M
(
10
)

4
M
(
2
.
5
)



s
s initial 
s
s  final
Which picture
matches
mathematical
description best?
Construct
a picture
thatthe
matches
the mathematical
description.
1.
2.
3.
4M
M
v  0m / s v  5m / s
4M
v  5m / s
4M
M
v  0m / s
M
v  5m / s v  0m / s
4M
M
v  2.5m / s v  10m / s
4M
v  10m / s
4M
M
v  2.5m / s
M
v  2.5m / s v  10m / s
A process is described with the momentum bar
chart shown below.
Pix + Ix
= Pfx
Construct
a verbal
description
thatthe
matches
the
Which verbal
description
matches
bar chart
bar
chart
shown above.
shown
above?
1.
2.
3.
Alan is riding a bike and hits a haystack, bringing him and his
bike to a stop.
Alan is riding his bike and hits a patch of ice where he slides
until he regains control and continues riding at a slower speed.
Alan gets hit by a tree branch and falls on the ground watching
his bike ride off in the distance.
AAsmall
smallperson
personisiswalking
walkingacross
acrossaamassive
massive
freely
picture
freelyfloating
floatinglog
login
inthe
thewater.
water. Which
Construct
a
represents
this process?
picture showing
the relative speed and
1directions
of
 the log and the person.
vperson
2

vraft
3

vraft

vperson
4

vperson

vperson
vraft
yo
y
A pendulum is seen swinging.
It hits a piece of clay at the
bottom. Use
Which
energy
verbal
and/or
description best
momentum
ideasmatches
to decide
the
pictorial
how
highdescription?
the pendulum rises
after the collision.
1 According to the conservation of energy, the increased mass
implies increased energy. y > yo.
2 Since energy is conserved, mass is not important. y = yo.
3 Momentum must be conserved when the pendulum hits the
clay, giving a smaller velocity, so y < yo.
4 There is no accurate way to determine how y and yo compare.
An object of mass 2 kg has a linear momentum
of magnitude 6 kg*m/s. What is this object’s
kinetic energy?
1.
3J
2.
6J
3.
9J
4.
12 J
5.
18 J
A ball of mass 0.5 kg, initially at rest, acquires a speed
of 4 m/s immediately after being kicked by a force of
strength 20 N. For how long did this force act on the ball?
1.
0.01 sec
2.
0.02 sec
3.
0.1 sec
4.
0.2 sec
5.
1 sec
A box with a mass of 2 kg accelerates in a straight line
from 4 m/s to 8 m/s due to the application of a force
whose duration is 0.5 sec. Find the average strength of
this force
1.
2N
2.
4N
3.
8N
4.
12 N
5.
16 N
A ball of mass m traveling horizontally with velocity v
strikes a massive vertical wall and rebounds back along
its original direction with no change in speed. What is
the magnitude of the impulse delivered by the wall to
the ball?
1.
0
2.
½ mv
3.
mv
4.
2mv
5.
4mv
Two objects, one of mass 3 kg and moving with a speed
of 2 m/s and the other of mass 5 kg and speed 2 m/s,
move toward each other and collide head-on. If the
collision is perfectly inelastic, find the speed of the
objects after the collision.
1.
0.25 m/s
2.
0.5 m/s
3.
0.75 m/s
4.
1 m/s
5.
2 m/s
Two objects move toward each other, collide, and separate.
If there was no net external force acting on the objects,
but some kinetic energy was lost, then
1. The collision was elastic and total linear momentum was conserved.
2. The collision was elastic and total linear momentum was not conserved.
3. The collision was not elastic and total linear momentum was conserved.
4. The collision was not elastic and total linear momentum was not conserved.
5. None of the above.
A rubber ball (mass = 0.08 kg) is dropped from a height
of 2 m, and after bouncing off the floor, rises almost to its
original height. If the impact time with the floor is
measured to be 0.04 sec, what average force did the floor
exert on the ball?
1.
0.16 N
2.
16 N
3.
25 N
4.
36 N
5.
64 N
Which of the following best describes a perfectly
inelastic collision free of external forces?
1.
Total linear momentum is never conserved.
2.
Total linear momentum is sometimes conserved.
3.
Kinetic energy is never conserved.
4.
Kinetic energy is sometimes conserved.
5.
Kinetic energy is always conserved.